The subject technology relates generally to DC-DC converters and specifically to isolated, bi-directional, DC-DC converters.
The electrification of transportation is developing more and more dynamically with time. Important objects of electrification are fuel economy, increased reliability of vehicles, increased life of vehicle and equipment, and reduction in vehicle cost. Power modules for vehicle electrification generally include DC-DC converters, motor drivers, energy storage (e.g. battery) and electromagnetic machines such as alternators, generators, and motors.
FIG. 1 shows a block diagram of one aspect of the subject technology. In this configuration, the alternator can be replaced by a starter-alternator, thereby making the system more powerful, more useful, and more reliable because a 48V starter has a much higher efficiency than a 12V starter, and will be more reliable.
One purpose of the subject technology is for use in bus transportation, in start-stop mode, but there are other applications. In one aspect, there are two modes of operation. The main mode wherein energy moves from a first battery (or alternator) at a first voltage (e.g. 48V), to a second battery at a lower, second voltage (e.g. 14.5V or 12V) and also to a high voltage port/load. The latter being capable of operative connection to various components (e.g. 3 phase DC-AC motor driver).
Whereas a conventional system would ordinarily be configured such that the 48V battery and the 12V battery have their negative terminals tied to the chassis of the vehicle, the subject technology provides internal isolation between these two batteries, which reduces parasitic transient circulation currents, filter cost, and reduced EMI. An advantage is therefore realized over existing topologies which are not sufficiently cost effective.
In a second step-down mode, energy from the high voltage port flows to the low voltage ports (e.g. 48V battery and 12V battery). The first mode is primarily a step-up mode (to the motor drive) and step-down (to the twelve volt system). In the second mode, the unit provides charge to the vehicle batteries, in a step-down mode.
In one aspect, the specifications are as follows. Main Mode: Vin=42-60 VDC, Vout=13.2-15 VDC @ 300 ADC, motor drive=10 kW/13 kVA, 3 phase 208 VAC, 50-60 Hz; Second Mode: input=3 phase, 208 VAC, 50-60 Hz, output=42-56 VDC @ 120 A, and 10.5-15 VDC @ 50 ADC, the efficiency of the power unit being 93% under full load in both directions.